1. Field
Embodiments of the present invention generally relate to semiconductor substrate processing systems. More specifically, the invention relates to a coil assembly along with gas delivery for a plasma processing system.
2. Background
The fabrication of microelectronic devices includes a number of different stages, each including a variety of processes. During one stage, a particular process may include transmitting plasma to the surface of a substrate, such as a silicon substrate, to alter the physical and material properties of the substrate. This process may be known as etching, which may involve the removal of materials to form holes, vias, and/or other openings in the substrate. Polymer deposition is generally used along with the etching to protect the side walls.
Many semiconductor devices are processed in the presence of plasma in a processing chamber. Inductively coupled plasma (ICP) is one type of plasma source used in semiconductor processing. An ICP reactor generates plasma in a processing volume by supplying high frequency electrical current to coils disposed outside the processing volume. ICP reactors are capable of generating high-density, low pressure plasma and relatively free of contamination. Studies have shown that silicon etch rate and polymer deposition rate are proportional to the plasma density.
FIG. 1 schematically illustrates a conventional ICP reactor 10. The plasma reactor 10 includes a chamber body 11 which defines an inner volume 15 for processing a substrate 12 therein. Processing gases are supplied to the inner volume 15 from a gas source 16. One or two co-axial helical coils 13, 14 are disposed outside the inner volume 15. The helical coils 13 and 14 are coupled to a high frequency power source 17 to provide time varying electric currents to the helical coils 13, 14 which generate electromagnetic field to breaks down processing gases and form plasma in the inner volume 15.
The inventors have discovered that improvements to the design of the gas delivery and the coil assembly in a plasma processing chamber have substantially higher plasma density and have a beneficial effect on plasma uniformity and power coupling to the outer region of the plasma.